Even though the novel revolves around a murder, the mood is generally as playful as it is suspenseful. Dr. Sheppard and Christie alike have a lot of fun with the reader. For instance, in Chapter 6, Inspector Davis asks Sheppard how he knows that he heard the silver table closing when he entered Ackroyd's house earlier. Sheppard complains to the reader about answering the question:
I was forced to explain in detail—a long, tedious explanation which I would infinitely rather not have had to make.
This line is funny because the reader knows that Sheppard loves explaining in detail the things he has observed. He loves it so much that he has written an entire account of the murder, which the reader has been taking in this whole time. In one sense, Christie seems to be inviting the reader in on a joke at Sheppard's expense: this man who claims to detest his sister's gossip habit and who claims to hate "long, tedious explanations" is the same person who is bringing the world an entire book full of gossip about the neighbor's murder. The tension is itself comical. It also allows the reader the pleasurable experience of reading a salacious story while looking down upon people like Caroline, who consume gossip without any sense of shame about it.
On another level, readers who might be returning to the book for a reread can see that Sheppard is playing as well. He claims that he is "forced to explain in detail" what he observed earlier, but he declines to repeat it for the reader. This could be because he doesn't want to bore the reader. As anyone who has already finished the book knows, however, Sheppard spends the entire book saying as much as he can without incriminating himself. His false modesty is a way of throwing the reader further off his track as a master manipulator who likes lying by omission.
